Pipes containing heat insulating material

ABSTRACT

The invention concerns the use of a material comprising at least a crosslinkable elastomer selected from the group consisting of butyl rubber, halobutyls and brominated isobutylene and para-methylstyrene copolymers, and at least a non-crosslinkable elastomer with low thermal conductivity for thermal insulation, in particular for pipes. The invention also concerns a pipe, and, in particular a submarine oil pipe for great depths, comprising at least a layer of said material.

The present invention relates to the use of a material based on acrosslinkable elastomer and on a noncrosslinkable elastomer of lowthermal conductivity for producing thermal insulation and in particularthe thermal insulation of pipes, in particular of undersea oil pipes,and to pipes which comprise at least one layer of this material.

The extraction of oil from undersea deposits requires the use of metalpipes, in particular for conveying the oil from the drilling site to theplace where it is recovered and optionally stored.

During drilling, the oil is extracted at a temperature of 70 to 120° C.During its transportation to the surface, it is cooled by thesurrounding seawater. In point of fact, it is essential for thetemperature of the oil extracted to be maintained at a value of greaterthan approximately 50° C., so as to prevent it from becoming too viscousand from setting solid in the pipes.

For their thermal insulation, pipes are currently composed of twocoaxial metal lines, between which is inserted a rigid foam,conventionally a polyurethane, or a material of syntactic type, namely arigid material, such as polyurethane, in which hollow glass microspheresare incorporated.

These pipes nevertheless exhibit the disadvantage of not being able tobe used below a depth of 200 to 300 meters, that is to say at a pressureof greater than 200 to 300 bar, beyond which pressure neither the rigidfoam nor the material of syntactic type offers sufficient mechanicalstrength.

Provision has also been made to have available, around oiltransportation pipes, heating systems consisting of water and gaspipework. Such systems are nevertheless too complex and expensive to besatisfactory from an industrial viewpoint.

The inventors therefore set themselves the aim of providing for amaterial of low thermal conductivity, capable of ensuring thermalinsulation and in particular the thermal insulation of undersea oilpipes, which overcomes the disadvantages of the thermal insulationsystems provided to date and which can be used down to depths of 3000meters.

Materials which comprise a butyl rubber in combination with apolyisobutylene are known from German patent application No. 2 408 152and from Japanese patent application No. 2 281 504. According to DE-A-2408 152, such a combination results in a material which is characterizedby a high mechanical dissipation capacity and which makes it possible todeaden the vibrations and noise and to improve the rubbing. InJP-A-2-281504, the material is provided in the form of wound sheets orstrips for insulating high-tension electrical cables.

These materials are under no circumstances described as capable ofproviding thermal insulation.

A subject matter of the present invention is the use of a materialcomprising at least one crosslinkable elastomer selected from the groupconsisting of butyl rubber, halobutyls and brominated copolymers ofisobutylene and of para-methylstyrene and at least one noncrosslinkableelastomer of low thermal conductivity for producing thermal insulation.

Within the meaning of the present invention and in that which follows,the term “low thermal conductivity” is understood to mean a thermalconductivity of less than or equal to 0.140 W.m⁻¹.K⁻¹, the latter beingmeasured using a device sold under the Anter trademark according to thestandard ASTM E 1530.

The term “halobutyl” is understood to mean both chlorobutyls andbromobutyls, such as chlorobutyl 1066 and bromobutyl x2, sold by Exxon.

Mention may be made, as examples of butyl rubber and of brominatedcopolymers of isobutylene and of para-methylstyrene which can be usedaccording to the present invention, respectively of butyl 365, sold byBayer, and Exxpro® 90-10, sold by Exxon.

The thermal conductivities of the elastomers exemplified above are ofthe order of 0.118 (for Exxpro® 90-10) to 0.125 W.m⁻¹.K⁻¹.

Said noncrosslinkable elastomer of low thermal conductivity present inthe material is advantageously a polyisobutylene. Mention may be made,for example, of Vistanex® MML 80 and Vistanex® MML 120, sold by Exxon,the thermal conductivities of which are respectively 0.122 and 0.125W.m⁻¹.K⁻¹.

According to an advantageous arrangement of the invention, the materialfurthermore comprises at least one thermoplastic of low thermalconductivity chosen from fluorinated thermoplastics and polyolefinicthermoplastics and at least one thermosetting plastic of low thermalconductivity.

Said polyolefinic thermoplastic consists, for example, of apolypropylene, while said fluorinated thermoplastic is advantageously aterpolymer of tetrafluoroethylene, of hexafluoropropylene and ofvinylidene fluoride, commonly known as THV and sold, for example, underthe names Dyneon® 400 and Dyneon® 500 by 3M. Its thermal conductivity isof the order of 0.140 W.m⁻¹.K⁻¹.

Furthermore, said thermosetting plastic of low thermal conductivity isadvantageously a polyimide, such as the Vespel® and Capton® polyimides,sold respectively by Du Pont de Nemours and 3M, the thermalconductivities of which are of the order of 0.120 W.m⁻¹.K⁻¹.

It is clearly understood that the material used in accordance with thepresent invention can also comprise, as is known in connection with anyformulation based on elastomers, an appropriate crosslinking system andvarious additives conventionally employed in the polymers industry, suchas, without implied limitation, activators (active zinc oxide, forexample), complexing agents (for example stearic acid), plasticizers(for example a naphthenic or paraffin oil), lubricants (for example apolyethylene glycol), processing aids (such as Crodamide® ER sold byCroda), or compatibilizing agents, such as an SEBS which may or may notbe modified by maleic anhydride.

A small amount of antimony oxide can also be introduced asnonreinforcing filler for better processability of the material, thisbeing achieved without influencing its thermal conductivity. This filleris advantageously introduced at a level of at most 50 parts by weightand preferably at a level of 20 parts by weight.

With regard to the abovementioned crosslinking system, it can be anysystem known in the polymers industry, such as a system for crosslinkingby organic peroxides, by metal oxides (active zinc oxide+DHT4A2+ZBEC,for example), by phenolic resins (brominated or nonbrominated phenolicresins, such as those sold by Schenectady under the references SP1045 orSP1055) or by sulfur donors, preferably not generating nitrosamine(Renocure® SG+Deovulc® BG 187 or Sulfadon® CLD+Deovulc® BG 187). Amongthese crosslinking systems, phenolic resins have proved to beparticularly well suited to the preparation of the material as they makeit possible to obtain highly satisfactory mechanical properties.

According to another advantageous arrangement of the invention, thematerial comprises:

-   -   between 30 and 120 parts by weight of said crosslinkable        elastomer,    -   between 20 and 100 parts by weight of said noncrosslinkable        elastomer,    -   between 0 and 100 parts by weight, preferably    -   between 20 and 100 parts, of said thermoplastic, and    -   between 0 and 100 parts by weight of said thermosetting plastic.

In a particularly advantageous way, the material used in accordance withthe invention exhibits a thermal conductivity of less than or equal to0.140 W.m⁻¹.K⁻¹, preferably of less than or equal to 0.130 W.m⁻¹.K⁻¹.

The material used in accordance with the invention exhibits theadvantages of being flexible, because of the presence of compounds ofelastomeric nature, and of exhibiting a particularly low thermalconductivity, as indicated above.

Surprisingly, they can be manufactured and processed in the absence ofreinforcing or nonreinforcing fillers, such as carbon black, silica,chalk and kaolin, fillers which are conventionally used in the polymersindustry and which increase the thermal conductivity of materials.

In addition, this material is compact, that is to say of noncellularnature, which confers on it an excellent resistance to pressure, aparticularly advantageous characteristic for its use at great underseadepths, as will be described in more detail subsequently.

According to yet another advantageous arrangement of the invention, thematerial additionally comprises hollow glass microspheres, for examplethe glass microspheres of 38/4000 grade sold by 3M.

The presence of these hollow glass microspheres makes it possible tolower the relative density of the material, from approximately 0.98 (intheir absence) to approximately 0.65, a fall in relative density whichis particularly advantageous for its floatability. These glassmicrospheres also contribute to a fall in the thermal conductivity ofthe material according to the present invention, a fall which becomesmore pronounced in proportion as the percentage by volume of glassmicrospheres increases, which percentage can reach 60% by volume. It isthus possible to obtain materials with a thermal conductivity of theorder of 0.09 W.m⁻¹.K⁻¹.

The incorporation of the hollow glass microspheres in the material canbe carried out using a twin-screw extruder, a first compartment of whichcomprises said microspheres and a second compartment of which compriseseither the combined ingredients of the material blended beforehand, inthe case of a process for the manufacture of the material as aconventional rubber, or the combined ingredients of the materialcrosslinked beforehand dynamically (namely simultaneously subjected tomixing and to stationary phases of increasing temperatures), in the casewhere the material is manufactured as a thermoplastic elastomer (whichis in particular the case when the material comprises a thermoplastic).

Silanes can also be used for the purpose of providing better bondingbetween the glass microspheres and the elastomers present in thematerial.

According to a preferred arrangement of the invention, the material isused for the thermal insulation of pipes.

Within the meaning of the present invention, the term “pipe” isunderstood to mean any tube, line, piping or the like for the conveyanceof fluids.

A particularly advantageous use of the thermal insulation materialaccording to the present invention is the insulation of undersea oilpipes, in particular of undersea pipes at great depth, for example at adepth of 2000-3000 meters.

Another subject matter of the present invention is a pipe, characterizedin that it comprises at least one layer of a thermal insulation materialas described above.

Such pipes comprise, for example, a metal tube coated on its externalface with a layer of the material according to the invention,advantageously with a thickness of 20 to 40 mm.

The pipes according to the invention can, in a particularly advantageousway, be used at depths of 2000 to 3000 meters without being deformed bythe pressures of 200 to 300 bar which prevail there, in contrast to thecurrently existing pipes, thus making possible the drilling of hithertoinaccessible oil layers.

In addition to the preceding arrangements, the invention also comprisesother arrangements which will emerge from the description which willfollow, which refers to examples of formulations of materials capable ofbeing used for thermal insulation, in particular of undersea oil pipesat great depth, and of measurements of their thermal conductivity. Itshould be clearly understood, however, that these examples are givensolely by way of illustration of the subject matter of the invention, ofwhich they do not in any way constitute a limitation.

EXAMPLE 1 Formulation, Preparation and Thermal Conductivity of a FirstMaterial for Thermal Insulation

The compounds used and their amounts, expressed as parts by weight, aresummarized below:

Butyl rubber 365 (Bayer) 30 Vistanex ® MML 120 (Exxon) 70 Naphthenic oil10 Active zinc oxide (HB Chemical) 5 Stearic acid 1 Phenolic resinSP1055 (Schenectady) 10

It is therefore a material based on a crosslinkable elastomer (the butylrubber) and on a noncrosslinkable elastomer of low thermal conductivity(the Vistanex® MML 120).

The material is prepared as a conventional rubber: the combinedcompounds are first placed in a mixer and then a stage of mixing iscarried out in accordance with the techniques known to a person skilledin the art in connection with rubbers. After a stage of forming thematerial, the latter is vulcanized using a compression molding press for15 minutes and at 180° C.

The thermal conductivity of the material thus obtained is 0.112W.m⁻¹.K⁻¹.

EXAMPLE 2 Formulation, Preparation and Thermal Conductivity of a SecondMaterial for Thermal Insulation

The compounds used and their amounts, expressed as parts by weight, aresummarized below:

Exxpro ® 90-10 60 Vistanex ® MML 80 20 Dyneon ® 400 20 Naphthenic oil 10Polyethylene glycol 4000 2 Crodamide ® ER 0.5 Active zinc oxide (HBChemical) 1.5 DHT 4A2 2 ZBEC 1.5

It is therefore a material based on a crosslinkable elastomer (Exxpro®90-10), on a noncrosslinkable elastomer of low thermal conductivity(Vistanex® MML 80) and on a fluorinated thermoplastic of low thermalconductivity (Dyneon® 400).

ZBEC corresponds to zinc dibenzyldithiocarbamate; this accelerator issold by Safic-Alcan. With regard to DHT 4A2, it corresponds to a mixtureof magnesium and aluminum oxides sold by Mitsui & Co. and also acts asaccelerator for the crosslinking.

In view of the presence of the fluorinated thermoplastic, the materialis prepared in the same way as a thermoplastic elastomer, that is to saywith dynamic crosslinking during the blending of the combinedingredients.

The compounds listed above are thus placed in a mixer, the temperatureof which is initially adjusted to 150° C., the speed of the rotors being95 revolutions/minute and the pressure of the piston being 3.5 bar. Thetemperature of the blend is gradually increased according to thefollowing protocol: at 1 minute, 135° C.; at 4 minutes, 210° C.; at 6minutes, 215° C.; at 12 minutes, 230° C. The blend is then cooled whilereducing the speed of the rotors and, when its temperature isapproximately 180° C., it is subjected to calendering to produce a sheetwith a thickness of 5 to 10 mm which is subsequently ground. The groundmaterial is again mixed on a twin-screw extruder and extruded at the dieoutlet in the form of granules, which granules can subsequently beformed in accordance with the wishes of the user.

The thermal conductivity of the material thus obtained is 0.125W.m⁻¹.K⁻¹.

EXAMPLE 3 Formulation, Preparation and Thermal Conductivity of a ThirdMaterial for Thermal Insulation

The compounds used and their amounts, expressed as parts by weight, aresummarized below:

Exxpro ® 90-10 100 Vistanex ® MML 80 50 Naphthenic oil 5 Polyethyleneglycol 4000 2.5 Crodamide ® ER 0.6 Active zinc oxide (HB Chemical) 2Renocure ® SG 3 Deovulc ® BG 187 2

It is therefore a material based on a crosslinkable elastomer (Exxpro®90-10) and on a noncrosslinkable elastomer of low thermal conductivity(Vistanex® MML 80).

This material is also prepared with dynamic crosslinking during theblending of the combined ingredients, according to a procedure similarto that described in example 2.

The compounds listed above are thus placed in a mixer, the temperatureof which is initially adjusted to 80° C., the speed of the rotors being100 revolutions/minute. When the temperature of the blend reaches200-230° C., the blend is cooled while decreasing the speed of therotors and, when its temperature is approximately 180° C., it issubjected to calendering to produce a sheet with a thickness of 5 to 10mm. This sheet is ground and the ground material is again mixed on atwin-screw extruder and extruded at the die outlet in the form ofgranules.

The thermal conductivity of the material thus obtained is 0.130W.m⁻¹.K⁻¹.

As emerges from the above, the invention is in no way restricted tothose of its implementations, embodiments and application forms whichhave just been described more explicitly; on the contrary, it embracesall the alternative forms thereof which can come to the mind of atechnologist in the subject, without departing from the context or fromthe scope of the present invention.

1. A method comprising: coating a pipe on an external face with at leastone layer of a composition comprising at least one crosslinkableelastomer selected from the group consisting of butyl rubber,halobutyls, brominated copolymers of isobutylene and brominatedcopolymers of paramethylstyrene, and at least one noncrosslinkableelastomer of low thermal conductivity.
 2. The method as claimed in claim1, wherein the noncrosslinkable elastomer of low thermal conductivity isa polyisobutylene.
 3. The method as claimed in claim 1, wherein thecomposition further comprises at least one thermoplastic of low thermalconductivity selected from the group consisting of fluorinatedthermoplastics and polyolefinic thermoplastics, and at least onethermosetting plastic of low thermal conductivity.
 4. The method asclaimed in claim 3, comprising a fluorinated thermoplastic terpolymercomprising polymerized units of tetrafluoroethylene, hexafluoropropyleneand vinylidene fluoride.
 5. The method as claimed in claim 3, comprisinga polypropylene.
 6. The method as claimed in claim 3, wherein thethermosetting plastic of low thermal conductivity is a polyimide.
 7. Themethod as claimed in claim 1, wherein the composition comprises between30 and 120 parts by weight of said crosslinkable elastomer, between 20and 100 parts by weight of said noncrosslinkable elastomer, between 0 to100 parts by weight of a thermoplastic, and between 0 and 100 parts byweight of a thermosetting plastic.
 8. The method as claimed in claim 1,wherein the composition has a thermal conductivity of less than or equalto 0.140 W.m⁻¹.K⁻¹.
 9. The method as claimed in claim 8, wherein thethermal conductivity is less than or equal to 0.130 W.m⁻¹.K⁻¹.
 10. Themethod as claimed in claim 1, wherein the composition further compriseshollow glass microspheres.
 11. A pipe comprising at least one layer of athermal insulation material comprising the composition of claim
 1. 12.The pipe of claim 11, wherein said pipe is an undersea oil pipe.
 13. Themethod as claimed in claim 1, wherein the composition is applied to apipe.
 14. The method of claim 13, wherein the pipe is an undersea oilpipe.
 15. A pipe comprising at least one layer of a thermal insulationcomposition comprising at least one crosslinkable elastomer selectedfrom the group consisting of butyl rubber, halobutyls, brominatedcopolymers of isobutylene and brominated copolymers ofpara-methylstyrene, and at least one noncrosslinkable elastomer of lowthermal conductivity, wherein the thermal insulation composition iscoated on an external face of the pipe.
 16. The pipe of claim 15,wherein the pipe is an undersea oil pipe.
 17. A method comprisingapplying to a substrate at least one layer of a composition comprising(i) at least one crosslinkable elastomer selected from the groupconsisting of butyl rubber, halobutyls, brominated copolymers ofisobutylene and brominated copolymers of paramethylstyrene, (ii) atleast one noncrosslinkable elastomer of low thermal conductivity (iii)at least one thermoplastic of low thermal conductivity selected fro thegroup consisting of fluorinated thermoplastics and polyolefinicthermoplastics, and (iv) at least one thermosetting plastic of lowthermal conductivity.
 18. A method comprising applying to a substrate atleast one layer of a composition comprising (i) at least onecrosslinkable elastomer selected from the group consisting of butylrubber, halobutyls, brominated copolymers of isobutylene and brominatedcopolymers of paramethylstyrene, (ii) at least one noncrosslinkableelastomer of low thermal conductivity, (iii) a terpolymer comprisingpolymerized units of tetrafluoroethylene, hexafluoropropylene andvinylidene fluoride and (iv) at least one thermosetting plastic of lowthermal conductivity.
 19. A method comprising applying to a substrate atleast one layer of a composition comprising (i) at least onecrosslinkable elastomer selected from the group consisting of butylrubber, halobutyls, brominated copolymers of isobutylene and brominatedcopolymers of paramethylstyrene, (ii) at least one noncrosslinkableelastomer of low thermal conductivity, (iii) a polypropylene and (iv) atleast one thermosetting plastic of low thermal conductivity.
 20. Amethod comprising applying to a substrate at least one layer of acomposition comprising (i) at least one crosslinkable elastomer selectedfrom the group consisting of butyl rubber, halobutyls, brominatedcopolymers of isobutylene and brominated copolymers ofparamethylstyrene, (ii) at least one noncrosslinkable elastomer of lowthermal conductivity, (iii) a polyimide and (iv) at least onethermoplastic of low thermal conductivity selected from the groupconsisting of fluorinated thermoplastics and polyolefin thermoplastics.